UNIVERSITY  OF  ILLINOIS 
LIBRARY 


Class 

9014, 


Book 


Volume 


My  08-15M 


UNIVERSITY  OF  ILLINOIS 
LIBRARY 


Volume 


When 


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A  GUIDE 


—  TO  THE  — 

^DALLES  OF  THE  ST.  CROIX^e^e 


.^.^FOR  EXCURSIONISTS  AND  STUDENTS-aMa* 


CHARLES  PETER  BERKEY,  Ph.  D.. 

INSTRUCTOR  IN  MINERALOGY  IN  THE  UNIVERSITY  OF  MINNESOTA. 


HINNEAPOLIS. 

THE  UNIVERSITY  BOOK  STORE. 


1898. 


317. 


GENERAL  view  of  the  ST.  CROIX  ABOVE  THE  DALLES. 


3 


GUIDE  TO  THE  DALLES  OF  THE  ST.  CROIX. 

LOCATION  AND  GEOGRAPHY. 

One  of  the  most  interesting  and  picturesque  localities  within  reach 
of  the  chief  centers  of  population  of  Minnesota  is  the  Dalles  of  the  St. 
Croix.  At  a  point  about  fifty  miles  northeast  of  Minneapolis  and  St. 
Paul  the  St.  Croix  river  has  cut  its  way  through  hard  igneous  rocks 
which  form  high  vertical  walls,  canyon-like  in  their  appearance,  and 
which  are  attended  by  many  rather  unusual  geological  and  physio¬ 
graphic  features.  The  most  extensive  outcrop  of  this  character  is  in  the 
immediate  vicinity  of  Taylor’s  Falls,  Minn.  Two  miles  farther  down 
the  river,  near  the  small  village  of  Franconia,  the  Lower  Dalles  may  be 
seen. 

The  St.  Croix  river  forms  the  boundary  between  Minnesota  and 
Wisconsin  at  this  point.  Communication  between  the  two  states  is  by 
means  of  a  toll  bridge — probably  the  only  one  of  its  kind  in  either  state. 
It  forms  the  connection  between  the  two  companion  villages,  Taylor’s 
Falls  and  St.  Croix  Falls,  one  on  either  side  of  the  river  just  above  the 
Upper  Dalles. 

Taylor’s  Falls  is  at  the  head  of  navigation  on  the  St.  Croix.  The 
old  boat  landing,  one  of  the  busiest  spots  in  the  early  days,  has  been 
almost  abandoned  for  many  years.  Before  railroads  were  constructed 
in  the  adjoining  territory,  when  river  boats  on  the  St.  Croix  and  Missis¬ 
sippi  carried  most  of  the  trade  of  a  growing  commonwealth,  this  place 
was  a  busy  commercial  center.  Mendota,  Stillwater,  Hastings,  St.  Paul 
and  Minneapolis  were  other  growing  towns  of  scarcely  greater  promise. 
Overland  shipping  by  rail  has  made  other  points  better  centers  of  distri¬ 
bution  and  the  natural  advantages  of  other  portions  of  the  state  have 
tended  to  move  population  and  trade  farther  westward. 

This  is  the  southern  limit  of  the  white  pine  as  well  as  the  southern 
limit  of  the  Keweenawan  rocks.  The  first  saw  mill  in  the  state  was 
located  only  a  few  miles  below  the  Dalles,  and  to  this  day  the  St. 
Croix  river  has  not  ceased  to  be  one  of  the  chief  driveways  for  pine. 

REFERENCE  BOOKS  AND  ARTICLES. 

The  following  references  contain  descriptions  of  the  Dalles  of  the 
St.  Croix  and  vicinity.  For  a  thorough  understanding  of  the  geology 


f 


16910 


THE  GREAT  LOG  JAM.— SIXTY  MILLION  FEET  OF  PINE  TIED  UP  AT  THE  DALLES. 


o 


of  the  district,  a  careful  study  of  the  references  given  will  be  found  most 
helpful. 

Chamberlin-Strong:  1880 — Geology  of  Wisconsin,  Vol.  Ill,  Pt. 
VI,  pp.  365  to  428. 

Winchell-Upham:  1888 — Minn.  Geol.  Surv.,  Final  Rep.,  Vol.  II, 
PP-  399  to  425- 

Upham:  1896 — Rep.  Com.  Interstate  Park,  Lecture,  pp.  45  to  60. 
Berkey :  1898 — Geology  of  the  St.  Croix  Dalles  (a  thesis),  88 


PART  I. 

GEOLOGIC  HISTORY. 

I  rv 

At  the  time  the  oldest  rocks  of  this  district  were  formed  the  greater 
part  of  Minnesota  and  Wisconsin  was  occupied  by  the  sea.  It  is  claim¬ 
ed  by  geologists  that  northeastern  Minnesota  and  northern  Wisconsin 
and  Michigan  then  formed  a  part  of  the  continental  area.  Toward  the 
west  and  south  the  expanse  of  open  sea  seems  to  have  been  very  great. 
The  rocks  formed  during  this  period  are  known  as  the  Keweenawan  or 
copper-bearing  rocks.  Good  outcrops  of  them  are  to  be  seen  in  the 
vicinity  of  the  Dalles.  They  are  basalts  or  old  lavas  chiefly. 

This  was  a  period  of  the  most  extraordinary  volcanic  activity. 
Lavas  were  poured  out  in  immense  sheets  from  great  fissures  in  the 
crust  of  the  earth  and  spread  out  over  thousands  of  square  miles  in  the 
Lake  Superior  region.  One  flow  after  another  was  poured  out — some¬ 
times  separated  by  a  short  period  of  erosion  and  its  accompanying  sedi¬ 
ments  of  sandstones  and  conglomerates,  and  sometimes  accompanied 
by  such  violent  explosive  outbursts  as  to  cover  the  entire  surface  with 
ashes  and  cinders  to  a  considerable  distance.  Such  materials  finally  ac¬ 
cumulated  in  a  fairly  definite  and  distinct  series  of  rocks  which  have  a 
total  thickness  of  several  thousand  feet.  The  Dalles  is  near  the  south¬ 
western  limit  of  this  formation. 

After  volcanic  action  became  more  subdued,  a  long  period  of  time 
elapsed  during  which  the  bare  rock  surface  was  exposed  to  the  destruc¬ 
tive  forces  of  erosion.  Ravines  and  gorges  were  cut  into  these  solidified 
lavas  with  such  persistence  and  success  that  hundreds  and  perhaps  in 
places  even  thousands  of  feet  in  thickness  were  worn  away  from  the  sur¬ 
face  of  these  rocks.  Ridges  and  valleys  may  still  be  seen  in  the  vicinity 
of  the  Dalles  showing  a  difference  in  elevation  of  more  than  500  feet. 


b 

The  time  required  for  such  erosion  is  the  measure  of  the  interval  be¬ 
tween  the  close  of  the  Keweenawan  and  the  beginning  of  deposition  of 
the  next  succeeding  or  Cambrian  rocks. 

At  the  close  of  this  erosion  period  the  continent  gradually  sank  be¬ 
neath  the  sea.  The  higher  ridges  stood  long  as  rocky  islands  and  head¬ 
lands  in  the  advancing  ocean.  Conglomerates  belonging  to  the  Cam¬ 
brian  age  were  formed  along  the  rock-bound,  wave-battered  shores,  as 
may  in  places  still  be  seen  in  the  vicinity  of  the  Dalles.  Farther  from 
the  shore  sands  accumulated  with  mud  and  the  shell  remains  of  many 
low  forms  of  animal  life,  which  all  together  were  formed  into  great  beds 
of  sandstone  and  shales.  They  may  be  seen  in  the  river  bluffs  both 
above  and  below  the  Dalles. 

These  sedimentary  rocks  are  of  immense  thickness  and  great  geo¬ 
graphic  extent.  They  covered  probably  all  of  the  area  of  the  Keweena¬ 
wan  rocks  which  preceded  them  and  stretched  several  hundred  miles  off 
the  southern  margin  of  the  primitive  continent.  How  thick  the  accu¬ 
mulation  finally  became  in  the  Dalles  is  left  largely  to  conjecture.  It 
certainly  covered  all  the  high  ridges  of  igneous  rocks  which  now  crop 
out  through  them,  and  there  may  have  been  several  hundred  feet  more 
which  have  since  been  worn  away.  The  comparatively  soft  sandstones 
and  shales  were  rapidly  cut  into  and  destroyed.  That  a  large  amount 
of  this  formation  was  in  the  long  ages  succeeding  carried  away  by  the 
streams  is  well  substantiated  by  a  study  of  surrounding  territory,  and 
that  certain  of  the  original  calcareous  and  shaly  formations,  by  the  dis¬ 
solving  power  of  percolating  water,  have  been  greatly  changed  from 
their  original  petrographic  character  is  equally  certain.  In  this  manner 
great  quantities  of  calcium  carbonate  have  been  carried  away  by  the 
waters  in  solution,  while  the  more  difficultly  soluble  constitutents  have 
been  left  behind,  forming  numerous  varieties  of  dolomites  and  shales. 

In  all  probability  the  continent  again  sank  beneath  the  sea.  But 
if  it  did,  there  are  no  corresponding  formations  now  left  to  record  the 
event  for  us.  Such  deposits,  if  they  did  exist,  have  been  wholly  remov¬ 
ed  by  later  erosion. 

Then  a  great  geologic  revolution — the  ice  age — came.  Immense 
streams  of  ice  in  great  sheets  scoured  their  way  through  valleys,  over 
ridges  and  across  all  merely  local  inequalities,  carrying  sand,  gravel 
and  boulders  many  miles  from  their  parent  ledges  and  scattering  them 
broadcast — a  wonderful  mixture — upon  the  land.  Such  debris  covers 
the  greater  portion  of  northern  United  States.  In  general  the  ice  inva¬ 
sion  came  from  the  north.  Tongues  from  the  central  masses  were  often 
deflected  from  their  southerly  course  by  uniform  local  conditions,  so 


I 


i 


we  have  glacial  debris  carried  eastward  and  westward  as  well  as  south¬ 
ward  from  original  localities. 

These  conditions  lasted  a  long  time — possibly  a  hundred  thousand 
years.  And  at  its  close — not  very  long  ago,  perhaps  twenty  thousand 
years — present  conditions  were  inaugurated.  The  climate  became  tem¬ 
perate  again.  Erosion  once  more  set  in.  Streams  sought  new  chan¬ 
nels.  Soils  accumulated  upon  the  deserted  surface  of  the  drift,  and 
the  physiography  of  the  northwest  began  to  be  what  it  now  is  or  finally 
will  become. 

POSITION  IN  THE  GEOLOGIC  SCALE. 


The  following  tabulated  column  will  give  a  better  idea  of  the  ver¬ 
tical  range  of  the  rocks  occurring  at  the  Dalles  than  any  mere  descrip¬ 
tion  is  likely  to  afford: 

Cenozoic  Era  (2,900,000  years) — 

Quaternary  period — Represented  by  recent  and  glacial 
deposits ,  in  the  Dalles  area,  200  feet. 


Tertiary  .  absent 

Mesozoic  Era  (7,240,000  years) — 

Cretaceous  . absent 

Jura-Trias  .  absent 

Paleozoic  Era  (17,500,000  years) — 

Carboniferous  .  absent 

Devonian  .  absent 

Silurian . absent 

Ordovician . absent 


Cambrian — Represented  f}y  sandstones,  shales,  dolomites 
and  conglomerates,  300  feet. 

Agnotozoic  Era  (17,500,000  years) — 

Keweenawan — Represented  by  numerous  lava  flows  and 
associated  breccias  and  volcanic  ash.  Appearing  at 
the  Dalles  as  a  massive  igneous  rock — diabase,  4,000 
feet. 

Animike . absent  or  not  exposed 

Keewatin . absent  or  not  exposed 

Archean  Era  (10,000,000  years) — 

Mareniscan  .  absent  or  not  exposed 

Laurentian . absent  or  not  exposed 


The  approximate  comparative  duration  of  successive  eras  are  esti¬ 
mated  in  years.  It  will  be  seen  that  only  a  small  portion  of  the  column 
is  represented  by  the  rocks  of  the  Dalles  area. 


IGNEOUS  ROCKS. 


ROADS  AND  STREETS.  •  FARM  HOUSES 


MAP  OF  THE  DALLES  AND  VICINITY. 
'Sixty  square  miles.) 


9 


PART  II. 

DETAILED  EXPLANATION  OF  LOCAL  GEOLOGY. 

l — Surface  Features  and  Recent  Geology, 

The  surface  features  and  contour  of  the  district  are  wholly  of 
glacial  origin,  modified  only  by  the  erosion  accomplished  by  the  pres¬ 
et  rivers  and  smaller  streams.  Bordering  the  river  on  the  west  is  a 
arge  and  comparatively  level  plain  of  till.  It  is  typically  developed 
n  the  vicinity  of  Franconia  station  on  the  St.  Paul  &  Duluth  railway 
is  one  enters  the  district.  Little  change  can  have  been  accomplished 
iy  post-glacial  agencies  on  this  particular  tract  beyond  the  drainage 
)f  a  few  shallow  lakes  and  sloughs  left  by  the  retreat  of  the  glaciers. 
Drainage  is  sluggish  and  largely  subterranean,  so  that  waters  which 
ink  into  the  soil  at  last  find  their  way  through  the  underlying  beds 
•f  sandstone  to  lower  levels  and  issue  as  springs  along  the  river  bluffs 
nd  other  places.  It  is  a  good  farming  district. 

The  adjacent  territory  in  Wisconsin  lying  just  east  of  the  river  is 
omparatively  rough.  It  is  also  of  glacial  accumulation,  but  of  a 
lifferent  type.  The  St.  Croix  moraine  lies  almost  parallel  to  the  river, 
nd  the  usual  characteristic  kettle-hole  contour  is  presented  in  perfec- 
ion  over  a  considerable  area.  Two  or  three  level  tracts  of  rather 
imited  extent  accompanying  this  moraine  belt  are  intimately  connected 
n  origin  with  local  conditions  prevailing  at  the  time  of  the  retreat 
)f  the  ice  sheet.  Most  conspicuous  among  these  is  the  terrace-like 
ract  bordering  the  river  just  east  of  St.  Croix  Falls,  and  also  the  glacial 
lood  plain  in  which  Dresser  Junction  is  situated.  The  former  lies  at 
.n  elevation  of  1,020  feet,  while  the  latter  is  nearly  100  feet  lower. 

But  the  feature  of  greatest  prominence  is  the  river  and  its  ac- 
ompanying  phenomena  of  erosion.  The  St.  Croix  river  has  cut  down 
nto  the  glacial  drift  and  underlying  rocks  from  two  to  three  hundred 
eet  below  the  average  elevation  of  its  territory,  and  more  than  400 
eet  below  some  of  the  igneous  ridges  which  outcrop  in  the  vicinity. 
Vs  one  enters  the  gorge  by  the  St.  P.  &  D.  Ry.,  immediately  upon 
eaving  Franconia  station,  the  whole  character  of  the  geologic  en- 
dronment  suddenly  changes.  Whereas  the  train  has  passed  for  an 
lour  through  a  level  and  monotonous  drift  district,  it  now  plunges  in 
ess  time  than  it  can  be  told  into  a  new  river  valley  where  every  con- 
our  has  been  chiseled  by  erosion.  Not  a  trace  of  the  original  drift 


10 


surface  can  be  seen.  Upon  entering  the  valley  this  proves  a  most  de- 
lightful  scenic  innovation,  and  its  study  a  most  interesting  and  in¬ 
structive  field  experience. 

B — River  Erosion. 

The  prominent  physiographic  features  presented  by  the  action  of 
the  river  are  terraces,  abandoned  channels,  river  lakes,  river  dams  and 
a  remarkable  accompaniment  of  the  erosion  of  the  igneous  rocks 
usually  known  as  pot-holes. 

( T1  Terrace:?.  There  are  five  terraces  to  be  seen  in  the  immediate 
vicinity.  At  about  905  feet  above  sea  level  the  first  or  highest  terrace 
forms  a  very  prominent  bench  which  is  known  in  Taylor’s  Falls  as  the 
picnic  ground.  It  also  occurs  in  more  limited  extent  on  the  Wis¬ 
consin  side  of  the  river  near  the  railway  station.  It  seems  to  be  closely 
associated  with  the  retreat  of  the  ice  from  the  vicinity.  Succeeding 


HOTEL  COCHECO,  DINING  ROOM.  TAYLOR  FALLS,  MINN. 

RATES  52.00  PER  DAY;  $6.00  TO  58.00  PER  WEEK 


ll 


ones,  however,  are  simple  river  terraces,  and  are  quite  as  easily  traced 
farther  down  in  the  gorge. 

The  second  terrace  follows  the  810  foot  contour  line  and  is  most 
easily  studied  on  the  east  side  of  the  river.  It  forms  a  comparatively 
narrow  bench  along  which  the  main  business  street  of  St.  Croix  Falls 
is  built,  and  may  be  traced  throughout  the  village. 

At  780  feet  on  the  east  side  of  the  river  a  third  terrace  is  developed 
to  a  considerable  distance  above  St.  Croix  Falls. 

At  750  feet  on  either  side  of  the  river  the  fourth  terrace  forms 
the  conspicuous  and  extensive  level  tracts  bordering  the  present  river 
channel,  50  or  60  feet  above  the  water  level.  The  business  portion  of 
Taylor’s  Falls  is  built  on  this  terrace,  and  River  street,  as  far  as  the 
upper  falls,  is  a  part  of  the  same  bench.  Also  on  the  east  side  of  the 
river  it  is  the  same  terrace  on  which  the  mill  is  built,  and  on  which 
the  abundant  spring  water  is  collected  to  furnish  its  power. 

A  fifth  terrace  at  725  feet  has  a  very  limited  development  near 
the  toll  bridge. 

(b)  Abandoned  Channels. — The  St.  Croix  river  has  been  turned 
from  its  present  course  several  times  in  its  late  history.  Two  aban¬ 
doned  channels  are  within  reach,  one  of  them  of  considerable  import¬ 
ance  and  interest.  A  small  side  channel  may  be  seen  in  the  north 
portion  of  Taylor’s  Falls  near  the  freight  depot.  A  large  and  well 
marked  one  extends  southward  from  the  elbow  in  the  Dalles.  It  is 
about  two  miles  long,  reaching  the  river  again  less  than  a  mile  above 
and  opposite  Franconia.  It  was  abandoned  at  the  800  feet  contour, 
100  feet  higher  than  the  present  river  level,  upon  reaching  a  bed  rock 
of  diabase,  which  made  deeper  erosion  along  its  course  extremely 
difficult  and  slow.  The  present  channel  lies  considerably  to  the  west, 
and  passes  almost  wholly  through  much  softer  sedimentary  rocks. 

At  a  much  later  stage  a  part  of  this  channel  immediately  next  to 
the  Dalles  was  still  used.  It  is  now  marked  by  the  river-lake  Thaxter, 
which  lies  in  the  old  channel  at  the  level  of  the  present  river.  At  that 
time  in  the  history  of  the  river  there  must  have  been  a  considerable  fall 
at  this  place,  where  the  water  pouring  over  the  igneous  rocks  plunged 
down  into  the  easily  eroded  sandstones  adjacent.  A  fall  of  50  feet,  and 
perhaps  100  feet,  seems  to  be  a  reasonable  estimate  upon  the  evidences 
of  filling  of  the  abandoned  lake  Thaxter  channel  and  accompanying 
phenomena  of  erosion.  The  precipice  forming  the  brink  of  the  aban¬ 
doned  falls  may  be  seen  a  little  off  the  road  leading  to  Thaxter  lake, 
just  below  the  elbow  in  the  Dalles.  The  entrance  to  this  channel  is 
about  50  feet  above  the  present  river. 


12 


(c)  Pot-holes. — At  the  Dalles,  and  also  a  mile  above  the  Dalles, 
there  are  a  large  number  of  deep  holes  called  pot-holes  worn  into  the 
hard  igneous  rocks.  They  are  forming  in  the  present  river  bed,  and 
are'  also  found  even  more  abundantly  on  the  terrace-like  benches  to 
an  elevation  of  more  than  50  feet  above  the  river  level.  They  seem 
to  have  been  an  accompaniment  of  the  destruction  of  these  persistent 
rock  barriers  from  the  beginning  of  river  erosion. 

In  their  best  and  most  typical  development  probably  few  localities 
in  America  are  more  favored  than  this.  And  in  few  places  also  is  the 
question  of  their  origin  more  clear  or*  their  history  more  intimately 
connected  with  other  geological  questions  of  considerable  local  im¬ 
portance.  It  seems  clear  from  a  study  of  the  locality  that  all  of  these 
holes  have  been  formed  by  swiftly  running  water,  whose  swirling 
eddies,  produced  by  the  unevenness  of  the  rock  floor,  have  carried 
loose  sand  and  gravel  round  and  round  so  persistently  that  great  holes 
have  been  literally  drilled  into  the  hard  crystalline  rocks  which  formed 
the  river  bed.  Each  hole  was  then  filled  with  a  rotating  column  of 
water  at  whose  top  the  onward  flow  of  the  river  furnished  power  enough 
to  keep  it  in  rotation,  and  at  whose  bottom  pebbles  and  sand  and 
boulders  rolled  round  and  round  year  after  year  and  century  after 
century — boring  the  hole  deeper  and  grinding  the  pebbles  smaller — 
until  the  river  deserted  its  task  or  accomplished  the  object  of  its  toil. 
Untold  thousands  of  pebbles,  imprisoned  in  these  great  mills  of  nature, 
ground  themselves  to  atoms  only  to  be  replaced  by  as  many  others 
swept  down  by  the  floods  as  were  those  which  preceded  them — all 
used  as  slaves  by  the  river  as  a  great  live  monster  to  grind  away  this 
defiant  obstacle  to  his  progress. 

And  when  were  all  these  made?  Only  yesterday.  Yesterday 
morning,  geologists  say,  the  great  glaciers  of  the  ice  age  were  be¬ 
ginning  to  melt  away.  Their  floods  have  left  only  here  and  there  so 
magnificent  a  record  of  their  existence  and  power. 

At  the  close  of  the  ice  age  the  St.  Croix  river  carried  an  immense 
volume  of  water  contributed  by  the  melting  ice  of  the  retreating 
glaciers.  And  it  was  also  at  that  time  the  outlet  of  Lake  Superior, 
when  that  lake  was  500  feet  deeper  than  it  is  now,  and  when  it  drained 
into  the  Gulf  of  Mexico  instead  of  into  the  Atlantic  Ocepn. 

C — Glacial  Geology. 

Glacial  accumulations  in  this  vicinity  belong  only  to  the  later 
part  of  the  ice  age.  Nothing  is  necessarily  referred  to  an  earlier  stage 
than  the  Wisconsin,  although  there  may  be  deposits  older  in  the  ad¬ 
jacent  territory.  The  glacial  debris  as  till  and  modified  drift  is  abun- 


18 


dant  here,  and  in  places  is  of  considerable  thickness.  It  is  distributed 
both  in  level  tracts  and  in  moraines.  The  range  of  hills  to  the  east 
of  St.  Croix  Falls  constitutes  a  typical  morainic  belt. 

There  are  three  easily  separable  subdivisions  in  the  mantle  of 
drift  which  covers  most  of  the  district.  The  first  or  earliest  differs 
from  the  second  both  in  character  and  time  of  accumulation,  while 
the  third  differs  from  the  first  only  in  time. 

The  first  or  underlying  sheet  of  drift  is  a  red  till,  the  so-called 


ONE  OF  THE  LARGEST  POT  HOLES. 


14 


eastern  diift  of  the  Minnesota  geologists.  It  is  in  many  places  40  to 

50  feet  thick,  and  is  sometimes  faintly  stratified  as  if  deposited  in  quiet 
water. 

The  second  or  middle  drift  is  gray  in  color,  calcareous  in  dis¬ 
tinguishing  character,  and  in  its  chief  exposures  is  a  typical  western 
till.  It  is  the  gray  or  western  drift  of  the  Minnesota  geologists. 

The  third  or  latest  drift  is  found  in  isolated  areas  on  the  west  side 
of  the  river,  and  forms  the  whole  of  the  moraine  on  the  east  side  of 
the  river,  beyond  which  no  western  material  has  yet  been  found. 

All  of  this  material  was  accumulated  where  it  now  lies  during 
the  ice  age,  and  most  of  it,  at  least,  at  its  very  close.  Pebbles  and 
boulders  may  be  gathered  at  many  places  which  must  have  been  carried 
one  or  two  hundred  miles  from  their  parent  ledges.  As  nearly  as 
can  be  learned  from  the  evidences  to  be  seen,  the  situation  must  have 
been  essentially  as  follows:  A  glacier  moving  southward  or  south¬ 
eastward  from  the  lake  region  pushed  across  the  district  into  Minne¬ 
sota  territory  to  an  unknown  distance,  spreading  out  and  leaving 
behind  upon  its  letreat  a  great  thickness  of  debris  brought  from  the 
iron-bearing  and  neighboring  districts,  and  which  is  because  of  its 
content  usually  of  a  red  color.  Later  a  similar  arm  of  the  great  west¬ 
ern  ice  sheet  from  the  Red  river  valley  pushed  in  toward  the  St.  Croix, 
spreading  the  western  drift,  which  carries  a  considerable  amount  of 
limestone  debiis  from  western  localities.  This  later  invasion  barely 
crossed  the  St.  Croix  river.  By  the  time  it  had  reached  the  Dalles, 
the  eastern  ice  advanced  again  to  dispute  its  progress.  As  a  result 
the  two  stood  probably  for  a  long  time  directly  opposed  to  each  other, 
at  times  one  encroaching  upon  the  territory  of  its  antagonist,  but  at 
last  both  1  etiring  from  the  scene,  while  in  the  gap  between  them  the 
post-glacial  St.  Croix  was  settled  into  its  present  course. 

The  river  gorge  is  post-glacial.  The  old  or  pre-glacial  channel 
is  yet  unknown.  It  may  have  passed  to  the  west  farther,  perhaps 
through  the  Chisago  lakes,  but  upon  the  retreat  of  the  western  ice 
invasion  the  old  channel  was  so  badly  filled  with  drift  that  the  new 
one  at  the  Dalles  became  permanent. 

D — Sedimentary  Rocks. 

Sandstones,  shales  and  conglomerates  of  upper  Cambrian  age  in¬ 
clude  all  of  the  typically  sedimentary  rocks  occurring  at  the  Dalles. 
But  in  adjacent  territory  southward  from  this  locality  later  formations 
occur  as  high  in  the  scale  as  the  Devonian  age.  Those  formations 
belonging  to  the  Cambrian  age  have  been  divided  on  petrographic 
grounds  into  two  series.  Formations  belonging  to  the  lowest  or 


15 


arliest  series  are  chiefly  sandstones  and  shales  ;  those  belonging  to 

he  next  later  series  are  chiefly  dolomites  and  associated  dolomitic 

hales  or  sandstone.  The  tabulated  double  series  is  formulated  below , 

eginning  with  the  latest  formations  belonging  to  them. 

f  Shakopee  dolomite— 65  It . absent 

,  .  I  New  Richmond  Sandstone — 20  ft . absent 

Magnesian  j  Qneota  dolomite — 75  to  175  ft . Osceala 

Series.  I  Jordan  sandstone — 75  to  200  ft . Osceola 

[St.  Lawrence  dolomites  and  shales  30-2.0  ft.  Osceola 

Basal  f  Franconia  sandstone — 100  ft . The  Dalles 

Sandstone  -J  Dresbach  shales — 150  ft . . The  Dalles 

Series.  !  Hinckley  sandstone— 0  to  1000  ft . not  exposed. 

Two  of  these  formations  may  be  examined  at  this  locality.  The 
Franconia  sandstone  is  a  white,  friable  quartz  sandstone  which  forms 
he  bluffs  along  the  St.  Paul  &  Duluth  railway  a  mile  below  Taylor’s 
.nails.  Almost  its  total  thickness  is  exposed  here.  It  contains  few 
ossils,  and  is  of  little  value  for  economic  purposes. 

The  Dresbach  formation  is  also  well  developed  here.  It  includes 
he  lower  shaly  beds  of  the  gorges  along  the  railroad  where  the  Fran- 
:onia  sandstone  w:as  studied,  and  it  also  includes  the  calcareous  beds 
:o  be  seen  above  the  Dalles  on  either  side  of  the  river  at  intervals  for 
several  miles.  Probably  the  best  exposures  are  within  a  mile  above 
die  Dalles.  These  shales,  where  there  is  a  considerable  content  of 
calcium  carbonate  carry  large  numbers  of  fossils.  Fine  specimens  of 
Lingulepis  pinniformis  Owen  (Lingulepis  acuminata  Conrad)  may  be 
easily  obtained.  An  interesting  shale  which  is  heavily  charged  with 
secondary  concretionary  pyrite  occurs  near  the  carding  mill  on  the 

west  side  of  the  river,  half  a  mile  above  the  toll  bridge. 

Perhaps  the  most  interesting  and  unusual  accumulations,  however, 

are  the  conglomerates  which  lie  in  contact  with  the  igneous  rocks  in 
several  horizons.  Thev  are  made  up  w7hollv  of  large  and  small  diabase 
boulders  and  pebbles  from  the  adjacent  cliffs  or  shores  and  the  inter¬ 
stices  between  them  are  filled  with  sand  and  other  finer  materials. 
The  cementing  matter  for  these  fragmentals  is  both  calcareous  and 
ferruginous — in  places  calcium  and  magnesium  carbonates  occurring 
in  great  excess,  while  in  others  ferric  oxide  constitutes  the  chief  ce¬ 
menting  substance. 

Conglomerates  of  comparatively  little  thickness  are  no  doubt  of 
considerable  extent  along  the  zone  of  contact  between  the  sedimentary 
and  the  igneous  rocks.  But  because  of  such  a  position  there  are 
necessarily  few  places  uncovered  by  erosion  so  as  to  exhibit  this  con¬ 
glomerate  in  its  best  development.  The  most  extensive  outcrop,  and 
the  one  most  easily  accessible  to  excursionists,  is  also  the  most  profit- 


Tpper  _ 

Cambrian 

locks. 


16 


T  eJ°  ®Xa™me-  11  ma>'  be  seen  at  the  crossing  of  Mill  street  wit 
tlie  Jst.  P.  &  D.  R.  R.  as  a  ragged  bluff,  showing  a  thickness  of  cor 
g  omerate  of  about  20  feet.  Following  it  along  to  the  brow  of  th 
11  exce  ent  specimens  may  be  obtained  where  the  road  passes  directl 
over  this  splendid  outcrop  of  conglomerate.  This  place  is  one  bloc 
southwest  from  the  public  school  building.  Another  outcrop  may  b 
seen  in  the  river  gorge  on  the  Wisconsin  side  nearly  a  mile  above  th 

?■  Stl"  another  IS  exposed  in  the  gorge  on  the  Minnesota  side 

two  miles  south  ot  Franconia  village.  It  rises  from  the  water  leve 
as  a  vertical  bluff  50  feet  high.  It  is  one  of  the  most  conspicuou 
landmarks  seen  from  the  river. 


c>t  the  boulders  of  these  conglomerates  show  much  watei 
wear,  such  as  might  be  produced  by  wave  action  along  the  shore 
Considerable  variety  of  mineral  content  is  sometimes  encountered 
Crystallized  calcite,  dolomite  and  copper  compounds  in  geodes  anc 

ssures  are  most  common.  In  these  conglomerates  are  also  fount 
sometimes  fossils  of  extremely  rare  types. 

E — Igneous  Rocks. 


1  he  Keweenawan  eruptives  are  the  most  ancient  rocks  outcroppin 

m  the  vicinity.  They  form  the  Dalles  and  are  abundantly  exposed  I 

the  adjacent  territory.  The  most  satisfactory  place  for  a  study  o 

these  rocks  is  in  the  village  of  Taylor’s  Falls  itself,  where  thev  forn 

t  ie  surface  over  a  large  area.  Important  data  bearing  upon  "the  in 

teresting  question  of  origin  and  subsequent  history  have  been  obtainec 

here  On  account  of  the  rare  opportunity  offered  for  the  study  of  ; 

number  of  structural  problems  under  so  favorable  conditions,  a  few 

questions  will  be  discussed  briefly  and  the  best  places  for  their  studi 
pointed  out.  J 


I. — Origin. 


.  hroughout  the  whole  extent  of  the  Keweenawan  rocks  as  seen 
at  the  Dalles,  there  are  but  two  kinds  of  rocks  as  to  method  of  origin 
and  those  two  probably  have  the  same  ultimate  source.  The  two  kinds 
are  (a)  the  compact  hard,  dark  green,  crystalline  rock  of  diabase  type 
\v  uch  forms  the  body  of  each  successive  flow,  and  which  constitutes 
a  most  the  whole  thickness  of  this  formation  ;  and  (b)  a  fine  or  coarse¬ 
grained  ash-like  or  brecciated  interbedded  fragmental  rock  which 
occurs  111  comparatively  thin  layers  or  beds  between  successive  lava 
flows.  .  Although  these  two  are  so  radically  different  in  method  of 
ormation,  they  are  not  always  easily  distinguished.  A  thorough  studv 
however,  of  type  specimens  of  each  and  a  comprehensive  understanding 

of  the  geologic  structure  of  the  formation  will  in  a  little  time  enable 
one  to  recognize  them  in  the  field. 


17 


As  to  the  ultimate  source  of  these  kinds  of  rock,  they  are  both 
alike  of  volcanic  origin,  one  a  sheet  of  molten  lava  poured  out  either 
from  great  fissures  or  immense  craters,  and  the  other  as  fine  ash  and 
bombs  originating  in  violent  explosions  from  active  volcanoes.  As¬ 
sociated  with  this  last  is  the  broken  and  shattered  material  usually 
formed  upon  the  surface  of  an  advancing  stream  of  solidifying  lava. 
This  in  places  forms  a  remarkably  fine  example  of  a  volcanic  breccia. 

During  the  time  of  accumulation  of  this  formation  the  area  was 
certainly  a  land  surface.  All  associated  evidences  of  water  action  are 
limited  to  surface  wash  such  as  might  arise  from  heavy  rain  storms 
which  usually  accompany  explosive  volcanic  activity.  Even  the  strat¬ 
ified  appearance  of  the  ash  accumulations  are  indicative  of  such  origin, 
rather  than  that  they  were  deposited  in  or  beneath  the  sea.  The  cen¬ 
ters  of  the  greatest  activity  were  probably  to  the  northeast,  where 


KOATIXG  IX  THE  DALLES. 


18 


this  same  formation  has  a  very  extensive  development  on  both  sides 
of  Lake  Superior. 

2. — Separate  Flows — or  successive  periods  of  activity. 

A  lava  flow,  i.  e.,  a  lava  stream  or  sheet  forming  a  unit  in  the 
series  and  belonging  to  a  single  period  of  eruption,  has  certain  con¬ 
stant  peculiarities  of  structure  which  it  is  essential  to  understand  at 
the  outset.  The  most  general  of  these  are  a  compact,  more  or  less 
completely  crystallized  lower  and  middle  portion,  and  a  vesicular  more 
or  less  glassy  or  felsitic  upper  portion.  Two  independent  flows  are 
separated  by  a  persistent  lateral  plane,  which  also  marks  the  accumu¬ 
lation  of  ash,  bombs  and  breccias.  When  a  formation  composed  of 
such  materials  belongs  to  a  remote  age,  as  in  this  case  to  the  Keweena- 
wan,  the  immense  time  which  has  since  elapsed  has  given  ample  op¬ 
portunity  for  much  alteration  or  metamorphism  of  the  rocks.  Their 
original  condition  is  indicated  only  by  secondary  products  and  struc¬ 
tures  which  require  intelligent  geological  interpretation.  In  the  pres¬ 
ent  condition  of  these  rocks,  as  they  appear  at  the  Dalles,  the  following 
characters  are  repeated  with  comparative  uniformity  in  each  successive 
flow. 

At  the  base  of  each  flow  the  rock  is  a  compact,  very  dark  green 
diabase.  It  is  thoroughly  crystalline,  commonly  lustre-mottled  in  the 
lower  and  middle  portions,  and  made  up  of  the  primary  minerals, 
augite,  plagioclase  and  magnetite,  with  or  without  the  secondary  min¬ 
erals,  quartz,  epidote  and  chlorite.  In  the  middle  of  the  flow  there  is 
little  change  from  this,  although  occasionally  there  is  a  considerable 
development  of  pseudo-amygdaloid.  Toward  the  top  of  each  flow 
there  is  commonly  a  vesicular  or  amygdaloidal  condition  of  the  diabase. 
The  color  is  yellowish  green.  Epidote  is  more  abundant  as  a  sec¬ 
ondary  mineral.  Quartz,  chlorite,  epidote,  calcite,  feldspar  and  actin- 
olite  are  secondary  in  amygdules  and  pseudo-amygdules,  and  also 
among  the  crystal  grains  as  alteration  products.  Vertical  jointing  is 
usually  most  pronounced  in  the  middle  and  lower  portions,  while  lat¬ 
eral  parting  is  most  persistent  at  the  surface  of  each  flow.  The  dis¬ 
covery  of  ash  at  several  points,  which  in  each  case  agrees  with  the 
subdivisions  as  defined  above,  confirms  the  conclusion  that  the  num¬ 
ber  of  times  this  group  of  characters  is  repeated  in  the  series  is  an 
accurate  measure  of  the  total  number  of  flows  poured  out  upon  the 
area. 

The  number  of  these  flows  exhibited  in  this  single  outcrop  at  the 
Dalles  is  about  ten.  Seven  of  them  are  readily  followed  on  the  west 
side  of  the  river  as  one  proceeds  from  the  elbow  in  the  Dalles  over 


Fig.  2.  —Profile  of  Igneous  Rocks  at  the  Upper  Dalles,  Taylor’s  Falls,  Showing  the  Separate  Flows. 


19 


o 

o 


00 

: 

o 


^0 

o 

o 


o 

o 

o 


Su'vmit 
(7th  flow.) 

Ash 


Lookout 
Knob 
(6th  flow.) 


Tuff  and 
Volcanic 
Breccia. 
Ash. 


School 

House 

Bench. 

(5th  flow.) 


Rail  Road 
Cliff. 

(3d  flow.) 


Devil's 

Bench. 

Ash. 


River  level 
in  the 
Dalles. 


Ash. 

River  Road 
Shelf. 


Top  of 

Cliff. 

Tuff. 


20 


the  successive  steps  spid  benches  to  the  public  school  building  and 
beyond.  The  average  thickness  of  each  is  from  30  to  50  feet.  All 
dip  at  a  lo^v  angle  toward  the  southwest.  In  general,  erosion  has 
produced  a  step-like  contour  which  proves  to  have  a  definite  relation 
to  the  fundamental  geologic  structure. 

1  he  key  to  this  separation  is  to  be  seen  along  the  street  leading 
to  the  steamboat  landing.  1  he  surface  of  one  flow  forms  the  bench 
on  which  the  street  is  located,  and  at  several  places  a  narrow  shelf 
rises  a  few  feet  above  the  street  level,  while  upon  it  the  next  succeeding 
flow  rises  as  a  perpendicular  cliff  50  feet  high.  Differences  between 
textures  and  other  characters  exhibited  by  the  top  and  base  of  two 
flows  in  contact  should  be  seen  at  this  place.  A  repetition  of  this 
association  under  less  favorable  conditions  for  satisfactory  observa¬ 
tions  may  be  seen  at  other  horizons,  both  above  and  below. 

3. — Volcanic  Tuff. 

1  his  is  a  name  applied  to  the  fragmental  material  accumulated 
between  and  associated  with  the  lava  flows.  The  most  extensive  de¬ 
velopment  of  this  rock  shows  a  thickness  of  about  20  feet  in  one  bed. 
One  block  west  of  the  public  school  building  is  the  best  place  to  study 
this  bed,  where  it  extends  along  the  strike  of  the  formation  entirely 
across  the  ridge. 

fuff  may  be  recognized  at  several  other  places  by  the  following 
characters,  some  of  which  are  present  in  every  occurrence.  It  is 
composed  of  both  very  fine  and  very  coarse  fragments,  which  are  so 
firmly  compacted  through  metamorphic  processes  as  to  present  a  hard¬ 
ness  and  general  appearance  similar  to  the  adjacent  diabase.  But 
upon  close  inspection  the  elastic  character  is  observable  at  many  places 
in  the  field,  and  under  the  microscope  many  specimens  show  a  similar 
origin  even  when  the  unaided  eye  can  detect  no  evidence  sufficient 
to  separate  them  from  the  altered  diabase.  The  coarser  fragments  of 
the  tuff  are  angular  pieces  of  igneous  rock,  which  frequently  exhibit 
a  vesicular  or  an  amygdaloidal  structure.  They  are  the  shattered  crust 
of  the  flows,  such  as  accumulate  upon  the  surface  of  solidifying  lavas 
while  in  motion.  Finer  grains  in  the  tuff  are  of  several  different 

types,  and  likewise  of  different  origin.  Many  individuals  show  con¬ 
siderable  wear  into  rounded  grains  of  a  size  not  very  different  from 

those  of  a  fine  sandstone,  while  others,  and  notably  the  smallest  or 
finest  particles,  are  angular  and  show  little  wear. 

Much  of  this  material  is  typical  volcanic  ash.  It  accompanies 
explosive  activity,  and  is  in  fact  the  only  evidence  of  such  violent 
volcanic  disturbance  found  in  the  district.  Grains  are  found  which, 


DEVIL’S  CHAIR.— A  PRODUCT  OP'  JOINTING. 


22 


when  examined  with  the  microscope,  exhibit  all  stages  from  a  glass 
through  its  devitrification  aspects  to  a  clearly  crystalline  condition 
similar  to  the  diabase  of  the  brecciated  portion.  Furthermore,  in  the 
alteration  or  metamorphism  which  has  taken  place  a  large  proportion 
of  the  fragments  are  now  completely  changed  from  a  glass-like  ob- 
siddian  to  grams  of  the  secondary  minerals,  quartz,  epidote  and  chlo¬ 
rite,  which  preserve  perfectly  the  original  outline. 

In  several  places  the  ash  exhibits  characteristic  banding  usually 
belonging  to  the  water  assorted  materials  of  sedimentary  rocks.  This 
was  probably  done  by  the  rain  storms  which  accompany  volcanic 
disturbances,  and  the  resulting  streams  are  no  doubt  responsible  for 
such  wear  of  fragments  and  grains  as  was  accomplished.  Look  for 
such  phenomena  on  the  pot-hole  bench  near  the  large  “wells.”  A 
much  better  place  is  at  the  intersection  of  Government  and  West 
streets  opposite  the  residence  of  Mrs.  R.  C.  Gray. 

4- — Lithologic  Varieties. 

Besides  the  tuff  just  described,  there  are  three  or  four  typical 

phases  of  the  crystalline  rocks  which  should  be  recognized  in  this 
vicinity. 

a.  Lustre-mottled  Diabase. — This  is  the  spotted  or  mottled  variety 
of  rock  which  is  so  common  in  the  lower  flows.  Its  internal  structure 
which  produces  this  peculiar  appearance  consists  of  crystals  of  the 
mineral  augite  occurring  in  areas  one-fourth  to  one-half  inch  in  breadth 
in  which  are  embedded  numerous  microscopic  crystals  of  one  of  the 
feldspars.  Ihis  is  the  so-called  “ophitic”  structure  of  petrographers. 
It  is  a  noted  character  throughout  the  copper  bearing  rocks  of  the 
Lake  Superior  region. 

b.  Porphyry.— In  the  higher  flows  especially  there  is  a  consid¬ 
erable  porphyritic  development  of  the  feldspar  constituent.  Many  of 
these  crystals  are  large,  two  or  three  inches  long,  and  very  abundant. 

In  color  they  are  much  lighter  than  their  matrix,  usually  flesh  red  or 
gray. 

L"  Amygdaloid.  This  is  a  vesicular  lava  whose  cavities  have 
been  filled  with  secondary  minerals.  It  forms  usually  the  surface  of 
a  flow,  and  the  original  cavities  which  characterize  it  are  due  to  the 
expansion  of  steam  or  other  gases  imprisoned  in  the  molten  lava. 

d.  Pseudo-amygdaloid.— It  is  a  rock  in  which  cavities,  resem¬ 
bling  those  of  a  true  amygdaloid,  have  been  produced  by  other  pro¬ 
cesses  since  solidification  and  have  subsequently  been  refilled  with 
similar  secondary  products.  This  rock  is  rather  common. 


l'HE  OLD  MAN  OF  THE  DALLES 


24 


F — Decay  of  Rocks. 

^one  of  the  rocks  of  this  area  are  now  in  the  original  condition 
which  they  presented  at  the  time  of  their  formation.  In  many  cases 
the  rock  as  it  now  exists  contains  little  of  its  original  make-up,  while 
in  others  of  course  there  is  not  a  great  change.  Water  and  air  have 
destroyed  and  carried  away  many  constituents  and  carried  in  and  built 
up  just  as  many  others.  Heat  and  pressure,  two  of  the  greatest 
agents  in  metamorphism,  seem  to  have  accomplished  little  here.  But 
water  has  done  wonders  in  these  changes.  It  has  dissolved  the  shells 
of  animals  that  were  buried  in  the  sandstones  and  deposited  the  matter 
again  around  the  grains  of  sand  or  on  the  river  bluffs  or  in  caves  or 
crevices  as  a  cement  or  as  travertine  or  as  crystallized  calcite.  It  has 
dissolved  iron  compounds  from  the  rocks  and  deposited  them  again 
in  beautiful  little  concretions  of  iron  pyrite  in  the  lower  shales.  It 
has  dissolved  various  elements  from  the  igneous  rocks  and  deposited 
them  again  as  perfect  minerals  in  the  form  of  chlorite,  epidote,  quartz, 
etc.,  in  the  amygdules  of  the  same  rock.  It  has  removed  minerals 
from  their  places  in  the  rock  and  at  once  replaced  them,  particle  for 
particle,  by  some  other  minerals  more  suitable  to  existing  surrounding 
conditions.  It  has  dissolved  a  mineral  from  one  place  and  carried  it 
to  another ;  it  has  destroyed  one  mineral  to  replace  it  by  some  other ; 
it  has  carried  away  one  substance  to  replace  it  by  several  ;  it  has  filled 
places  where  there  was  nothing  before,  and  created  cavities  where 
there  is  nothing  now — all  so  promiscuously  that  it  might  seem  an 
accident,  but  all  in  very  fact  in  accord  with  the  most  unyielding  laws 
of  nature.  4  he  change  is,  in  general,  from  an  unstable  (easily  decayed) 
rock  to  a  comparatively  stable  one.  So  that  some  of  these  rocks, 
once  a  black,  glassy  basalt,  composed  of  feldspar,  pyroxene  and  mag¬ 
netite,  are  now  dark  green  crystalline  rocks  composed  of  quartz,  epi- 
dotc  and  chlorite.  While  the  original  rock  was  rather  readily  at¬ 
tacked  by  agents  of  decay,  the  green  product  now  in  its  place  is  com¬ 
paratively  indestructible  by  such  processes.  But  the  changes  are  not 
complete.  These  rocks  which  seem  so  unchangeable  are  in  reality 
changing  from  year  to  year,  as  they  have  always  done  in  all  the  cen¬ 
turies  that  have  already  passed. 

G— Minerals. 

Although  there  are  many  different  minerals  present  in  the  rocks 
in  the  vicinity  of  the  Dalles,  few  of  them  are  developed  into  good 
specimens  of  any  particular  species.  4  hose  which  are  represented  by 
some  characteristic  association  are  given  below: 

Calcite — In  clusters  of  nail-head  and  dog-tooth  crystals  filling  cav- 


25 

i ties  and  fissures  in  the  conglomerates.  Also  often  beautiful  travertine 
along  the  river  bluffs  from  Franconia  southward. 

Dolomite — Pearl  spar  crystals  are  rather  abundant  in  the  conglom¬ 
erate  outcrops  near  the  Dalles. 

Copper — Small  amounts  of  native  copper  in  the  igneous  rocks  may 
be  found  in  some  places.  Small  quantities  of  other  compounds  of  cop¬ 
per  also  occur. 

Pyrite — In  fine  concretions  about  the  size  of  a  pin  head  may  be 
found  in  the  lower  shales  near  the  carding  mill  in  Taylor's  Falls. 

Quartz — As  sandstone  it  is  very  abundant.  As  an  amygdule  filling 
resembling  agate  is  found  rather  sparingly,  and  crystallized  in  cavities, 
also,  occasionally.  As  a  secondary  mineral  scattered  miscellaneously 
through  the  rocks  it  is  very  abundant. 

Feldspar — An  original  constituent  of  the  igneous  rocks  is  abun¬ 
dant,  especially  in  the  porphvritic  varieties.  It  is  also  developed  as  a  sec¬ 
ondary  mineral  with  quartz  and  epidote  in  some  cavities. 

Epidote  is  the  yellowish  green  mineral  so  abundant  as  a  secondary 
product  in  the  igneous  rocks. 

Chlorite  is  the  dark  bluish  green  secondary  mineral  accumulated 
most  abundantly  in  amygdules  and  pseudo-amygdules. 

Hematite — This  oxide  of  iron  is  accumulated  in  some  of  the  joints 
of  the  diabase  in  the  railway  cut  near  the  Taylor’s  Falls  station,  and  is 
abundant  as  a  stain  at  many  other  places.  It  also  produces  abundant 
brown  veins  in  the  sandstone. 

Other  minerals  in  smaller  amount  or  less  conspicuous  in  obtaina¬ 
ble  specimens  are  augite,  magnetite,  kaolin,  apatite,  malachite,  azurite, 
actinolite. 

H — Life  History. 

■ 

One  of  the  most  interesting  questions  in  the  study  of  any  period 
or  the  exploration  of  any  area  is  the  determination  of  the  life  record. 
This  is  usually  preserved  in  a  very  broken  way  by  fossil  remains.  It  is 
incomplete  because  of  the  method  of  preservation  of  all  these  forms  of 
life,  and  especially  because  many  forms  must  have  existed  which  could 
not  be  preserved  at  all.  And  broken  because  we  can  reach  those  which 
are  preserved  only  here  and  there  in  a  limited  cut  or  quarry  or  river  bluff 
where  the  rocks  which  buried  them  have  been  disturbed. 

It  is  found  in  general  that  the  higher  forms  of  life  have  existed  only 
in  comparatively  recent  times ;  that  the  farther  back  in  the  geologic 
scale  we  go,  the  lower  in  the  life  scale  the  general  aspect  of  the  fauna 
descends ;  and  that  in  the  oldest  rocks  no  traces  of  life  are  found  at  all, 
showing  either  that  no  forms  of  life  existed  or  that  those  which  did  ex- 


st  were  so  simple  and  so  fragile  as  to  be  utterly  destroyed  by  the  ordi- 
lary  processes  of  fossilization. 

So  at  the  outset,  if  we  wish  to  enter  upon  a  study  of  the  life  record 
n  the  rocks  of  this  locality,  it  will  be  well  to  glance  once  more  at  the 
:able  of  rock  formations  and  geologic  periods  represented  here.  It  will 
De  found  that  there  are  only  three  periods  represented — the  Glacial,  the 
Cambrian  and  the  Keweenawan.  Of  these  the  glacial  period  need  re¬ 
ceive  no  further  attention  because  it  is  so  recent  that  it  represents  es¬ 
sentially  the  present  fauna  and  flora,  except  for  the  migrations  which 
accompanied  it.  The  rocks  of  the  Keweenawan  are  eruptives  in  this 
i locality  and  are  therefore  unfavorable  for  the  preservation  of  fossils  of 
any  kind.  It  is,  however,  of  interest  to  note  that  no  well  recognized  fos¬ 
sils  have  yet  been  credited  to  the  Keweenawan  or  to  any  earlier  forma¬ 
tion  from  the  Keweenawan  to  the  base  of  the  geologic  scale. 

Of  the  Cambrian  rocks,  which  are  also  represented  at  the  Dalles, 
more  should  be  said.  Characteristic  fossils  of  the  Cambrian  the  world 
over  are  trilobites,  which  are  crustaceans  of  a  crab  or  crayfish-like  struc¬ 
ture  or  appearance,  brachiopods,  which  are  molluscoidea  with  a  two- 
valve  shell,  and  gasteropods,  which  are  mollusca  of  a  snail-like  general 
appearance.  All  of  them,  however,  are  probably  lower  forms  structurally 
than  those  to  which  I  have  likened  them.  All  three  of  these  types  of 
lossils  are  represented  in  this  district,  and  one  of  them  at  least,  Lingu- 
lcpis  acuminata  Con.  ( Lingulepis  pinniformis  Owen),  is  so  abundant  that 
no  one  need  fail  in  obtaining  good  specimens.  Another,  Obolella  polita 
Hall,  is  rather  common.  These  are  well  known  typical  Cambrian  brach¬ 
iopods. 

Trilobites  are  less  common,  but  may  usually  be  obtained  in  the  con¬ 
glomerates  and  associated  sandstones.  At  Franconia,  in  the  sandstone 
quarried  there,  large,  good  specimens  may  sometimes  be  obtained. 

Fossils  of  the  gasteropod  type  are  rare  and  of  great  interest.  They 
represent  apparently  the  primitive  forms  of  this  group  of  animals  in  its 
early  formative  period.  For  example  specimens  may  be  secured  which 
are  perfectly  straight  like  a  cone,  others  that  are  curled  over  a  little  for¬ 
ward  or  backward,  and  still  others  which  are  fully  coiled  up  like  an  or¬ 
dinary  snail.  The  gradation  from  one  to  the  other  is  now  so  complete 
as  represented  by  specimens  in  my  private  collection  that  there  can  be 
little  doubt  of  their  close  relationship.  It  is  not  necessary  to  speculate 
as  to  how  the  primitive  gasteropod  on  the  seashore  at  Taylor's  Falls 
came  to  know  that  a  coiled  shell  or  house  would  be  of  more  use  to  him 
than  a  straight  one ;  or  indeed  whether  or  not  some  change  in  local  con¬ 
ditions  may  have  coiled  his  shell  for  him  in  spite  of  his  wishes. 


28 


On  the  whole  the  fossils  found  at  the  Dalles  form  a  unique  grouj 
in  the  paleontology  of  the  Cambrian  age. 

PART  HI. 

LOCAL  GEOLOGICAL  EXCURSIONS. 

Several  short  local  excursions  have  been  planned  for  those  who  car 
spend  but  a  short  time  at  the  Dalles  and  for  those  who  are  interested  in 
particular  features  which  they  wish  to  examine.  The  object  is  to  out¬ 
line  trips  requiring  from  one  to  two  hours  to  a  full  day’s  time  in  the  field 
for  each  one,  suggesting  the  order  of  points  to  be  visited  and  noting  the 
geologic  or  physiographic  features  worthy  of  attention.  References 
are  also  made  to  pages  m  the  text  where  more  complete  explanation  is 
given.  The  hotels  in  Taylor’s  Falls  are  centrally  situated  for  most  of 
these  short  excursions  and  each  trip  is  therefore  begun  and  ended  there 
For  tia\  eleis  spending  but  one  day  at  the  Dalles,  not  more  than  two  or 
three  of  these  side  trips  can  be  made  with  moderate  exertion.  In  order 
to  see  to  advantage  some  of  the  most  interesting  phases  of  local  geology 
much  climbing  is  inevitable.  To  reach  many  points  of  importance  long 
walks  or  drives  are  necessary. 

Wherever  practicable  the  time  usually  required  to  reach  points  and 
return  is  indicated.  Each  separate  trip  is  given  a  name  suggested  by 
the  geologic  feature  of  chief  prominence  to  be  seen. 

SHORT  EXCURSIONS. 

L  In  the  Dalles.  Pot-hole  Erosion  (one  or  two  hours). 

II.  Keweenaw  an  Lava  Flows.  Volcanic  Ash  and  Breccia  (tuff) 
(two  or  three  hours). 

III.  Cambrian  Conglomerates  and  Sandstones  (tv^o  hours). 

IV.  The  Glacial  Drift.  Eastern  and  Western  till  (one  hour).  - 

V.  River  History.  Terraces  (two  hours). 

VI.  River  History,  halls  and  Abandoned  Channels  (two  or  three 
hours). 

VII.  The  St.  Croix  Moraine.  Drift  Accumulations  (one-half  day). 

VIII.  The  Lower  Gorge.  A  river  trip  to  Osceola  (one  day). 

IX.  The  Lower  St.  Croix.  From  the  Dalles  to  Stillwater  (one  day). 

X.  Paleontology.  Fossils  and  their  Preservation  (one  day). 
COMBINATION  TRIPS  FOR  LARGE  O  NE-DAY  EXCURSIONS. 

XI.  Combination  No.  i.  Including  the  chief  features  of  II,  III  and 
IV  above. 

XII.  Combination  No.  2.  Including  the  chief  features  of  I,  V  and 
VI  above. 


Vss 


CEWEE- 

CAMBRIAN 

CAMBRIAN 

STREETS. 

EASTERN 

NAWAN 

CON¬ 

SANDSTONES 

DRIFT. 

•IABASES. 

GLOMER¬ 

AND 

ATES. 

SHALES. 

WESTERN  ALLUVIUM. 
DRIFT. 


GEOLOGICAL  MAP  OF  THE  IXTER-STATE  PARK  AT 

OF  THE  ST.  CROIX. 


THE  DALLES 


(An  area  two  miles^square  drawn  on  a  larger  scale. 

The  Inter-State  Park  boundary  on  the  west  side  ot  the  river  is  indicated  by  a  broken  line.) 


30 


SHORT  EXCURSIONS  OUTLINED. 

EXCURSION  I. 

In  the  Dalles.  Pot-Hole  Erosion.  (Time  one  or  two  hours.)  Pp.  12-13. 

Flan.  Start  from  the  hotels.  Go  one  block  east,  turn  south  and 
follow  the  street  to  the  steamboat  landing  in  the  Dalles.  The  district  tc 
be  studied  lies  between  this  street  and  the  river.  It  may  be  explored 
thoroughly  in  the  time  indicated  as  it  covers  but  three  blocks  at  most. 
Follow  the  many  foot  paths  through  the  pot-hole  district. 

Suggestions.  Note  the  separation  plane  between  two  lava  flows 
along  the  street  within  a  block  or  less  of  the  landing.  Examine  the  per¬ 
pendicular  wall  constituting  the  next  flow.  A  lower  flow  may  be  seen 
later  over  at  the  river  at  the  level  of  the  toll  bridge.  Examine  the  nu¬ 
merous  pot-holes.  Large  ones  are  situated  in  the  lower  portion  of  the 
district  near  the  angle  of  the  river.  Note  the  different  phases  of  the 
rock  about  them  amygdaloid  and  highly  altered  epidotic  varieties.  A 
bed  of  volcanic  ash  may  be  seen  near  the  largest  pot-holes  and  another 
of  very  limited  extent  near  the  toll  bridge. 

Examine  the  grinders  taken  from  the  holes;  some  very  large  ones 
may  be  seen.  Note  that  in  many  places  the  dividing  walls  between  two 
or  more  pot-holes  have  been  worn  away,  forming  large,  irregular  cavi¬ 
ties.  A  narrow  gorge  entirely  crossing  the  lower  end  of  the  district  has 
been  formed  in  this  way  by  the  destruction  of  the  thin  walls  between 
rows  of  large  pot-holes.  Observe  that  the  position  of  most  of  the  pot¬ 
holes  is  such  as  to  be  subjected  to  great  force  from  running  water. 

EXCURSION  II. 

The  Keweenaivan  Lava  Flows.  Volcanic  Ash  and  Breccia  (tuff).  (Time 
two  or  three  hours.)  Pp.  18-22. 

Plan.  Start  at  the  toll  bridge.  Pass  across  the  pot-hole  district  to 
the  steamboat  landing,  thence  up  over  the  successive  cliffs  to  the  public 
school  building  and  still  farther  west  to  the  limits  of  the  igneous  rocks. 
Distance  one-half  mile.  Rise  350  feet. 

Observations.  One  flow  at  the  toll  bridge  level  is  represented  by  a 
row  of  ledges,  upon  one  of  which  the  toll  gate  is  built.  Another  is 
prominent  at  the  street  level  300  feet  north  of  the  steamboat  landing, 
another  50  feet  higher  on  the  bench  just  below  the  railroad,  another  rep¬ 
resented  by  the  ledges  through  which  the  railway  is  cut,  again  one  just 
below  the  public  school  building,  and  the  most  interesting  one  of  all 
from  the  comparatively  level  tract  or  bench  on  which  the  schoolhouse  is 
built. 


FIG.  3.— VOLCANIC  TUFF. 

(MAGNIFIED  40  DIAMETERS.  ) 


(  “The  figure  is  from  a  microphotograph  of  a  section  of  the  volcanic  tuff  trom 
Taylor's  Falls.  Diabasic  characters  are  shown  by  the  darker  grains  in  the  figure 
nd  one  fragment  especially  at  the  right  side  exhibits  a  coarser  texture  th  n  is 
isual.  Several  grains  near  the  lower  margin  of  the  field  are  devitrified  glasses, 
n  grains  of  this  character  flowage  is  sometimes  prominent.  The  light  colored 
ragments  throughout  the  field  are  now  chiefly  quartz.  But  these  almost  all  show 
heir  secon  lary  character  by  the  penetration  of  actinolite  needles  which  project  in 
jeautiful  clusters.  Finer  fragments  of  a  more  angular  outline  lie  between  the 
arger  grains.”)  Berkey, — The  American  Geologist,  March,  1898. 

Examine  tbie  volcanjc  ash  and  breccia  (tuff)  which  is  prominent  one 
olock  farther  west.  Its  thickness  here  is  at  least  20  feet  between  succes¬ 
sive  flows  and  represents  either  an  interval  of  excessive  disturbance 
md  explosive  activity  or  a  much  greater  time  break  to  allow  the  accu¬ 
mulation  of  so  much  debris.  Splendid  specimens  of  fine  ash  or  water 
worn  material  or  breccia  may  be  obtained  along  this  bed. 

Other  subdivisions  of  the  formation  may  be  recognized  in  a  similar 
manner  at  higher  horizons.  Estimate  dip  and  thickness.  Note  recur¬ 
rence  of  structural  and  mineralogical  characters — porphyritic,  ophitic 
lustre-mottled)  and  amygdaloidal  phases,  the  accumulation  of  ash  as 
reparation  planes,  jointing,  alteration  and  secondary  products. 


32 


EXCURSION  III. 

Cambrian  Conglomerates  and  Sandstones.  (Time  two  hours.)  Pp.  14-16. 

Plan.  Start  at  the  schoolhouse.  Go  south  on  Mill  street  one  block. 
Follow  the  street  down  the  hill  to  the  railroad,  thence  along  the  tracks 
to  the  first  trestle  bridge  and  return  by  way  of  the  tracks  to  the  depot. 

Suggestions.  §top  at  the  brow  of  the  hill  to  see  the  magnificent 
outcrop  of  conglomerate  in  contact  with  the  diabase.  It  has  an  iron 
oxide  cement.  Examine  into  the  nature  of  the  boulders  of  which  it  is 
composed.  Get  a  good  specimen.  Note  that  occasionally  a  “tuff”  boul¬ 
der  is  included  in  the  conglomerate  among  the  others.  What  bearing 
has  such  observation  upon  the  comparative  ages  of  the  two  formations? 
Follow  the  outcrop  down  the  hill  and  halt  again  near  the  railroad  cross¬ 
ing.  This  is  the  celebrated  Taylor’s  Falls  outcrop  of  Cambrian  con¬ 
glomerate.  Calcium  and  magnesium  carbonates  with  sand  serve  as  a 
matrix  and  cement  here.  Good  small  crystals  of  each  may  be  found. 
Fossils  are  readily  found.  Rare  types  of  trilobites  and  gasteropods  are 
sometimes  secured. 

This  is  a  famous  locality  among  geologists  as  showing  the  “uncon¬ 
formity”  of  the  Cambrian  upon  the  Keweenawan  series.  Study  the  place 
so  as  to  comprehend  the  situation  which  it  represents  at  the  time  these 
conglomerates  were  formed. 

Pass  on  along  the  railroad.  Note  the  change  rapidly  to  a  finer 
grained  and  friable  sandstone.  Complex  veining  due  to  infiltrated  iron 
oxide  is  seen  in  the  sandstone.  This  is  the  Franconia  Sandstone  forma¬ 
tion. 

EXCURSION  IV. 

The  Glacial  Drift.  Eastern  and  Western  Till.  (Time  one  hour.)Pp.  12-14. 

Plan.  Start  from  the  hotels.  The  place  to  be  examined  is  along 
the  road  which  passes  under  the  trestle  and  up  the  ravine  bordering  the 
“picnic  ground.” 

Explanation.  Red  till  partially  stratified  as  if  deposited  in  water  lies 
at  the  base  of  the  drift  about  50  feet  in  thickness.  It  is  the  so-called 
“eastern  drift.”  It  is  succeeded  above  by  a  thin  bed  of  sand  and  gravel, 
which  is  known  as  “modified  drift.”  Above  still  farther  the  blue  or  gray 
till,  “western  drift,”  completes  the  accumulation  to  the  soil  cap  which 
forms  the  covering  of  the  “picnic  ground.” 

Note  the  characters  of  these  three  kinds  of  drift  and  the  two  kinds 
of  till  represented  especially.  They  are  as  perfect  examples  of  the  kinds 
of  drift  covering  Minnesota  as  can  be  found  any  place. 

Red  till  is  seen  again  higher  up  and  several  blocks  farther  west, 


33 


ear  the  Swedish  church.  It  was  deposited  probably  later  than  the  gray 
11  of  the  “picnic  ground, ”  so  that  wTe  have  in  all  three  separate  sheets  of 
11  represented  at  this  locality.  Most  places  on  the  opposite  side  of  the 
ver  only  one  can  be  made  out. 

XCURSION  V. 

'ivcr  History.  Terraces  and  Erosion.  (Time  two  or  three  hours.)  P.  io. 

Plan.  Start  from  the  hotels,  Taylor’s  Falls.  Cross  the  toll  bridge, 
'ollow  the  wagon  road  to  the  upper  falls,  where  the  igneous  rocks  oc- 
ur  in  the  river  again.  Return  by  way  of  the  principal  business  street  of 
t.  Croix  Falls. 

Observations.  The  hotels  at  the  beginning  are  on  a  river  terrace 
rhich  may  be  followed  for  a  distance  of  a  mile  on  the  Minnesota  side  of 
le  river.  At  places  it  is  very  level  and  has  a  width  along  River  street 
f  about  two  blocks.  It  is  the  fourth  river  terrace.  It  has  a  correspond- 
1  g  development  on  the  Wisconsin  side  of  the  river  along  the  wagon 
Dad  where  the  springs  are  so  abundant  and  where  the  flour  mill  is  lo- 
ated.  A  lower  terrace  is  represented  by  small  areas  near  the  toll  bridge, 
'he  main  business  street  of  St.  Croix  Falls  is  built  upon  the  second  ter- 
ace.  It  can  be  followed  throughout  the  village.  The  highest  terrace 
long  the  St.  Croix  at  this  point  is  at  905  feet.  It  is  observable  on  both 
ides  of  the  river,  but  is  especially  prominent  on  the  Minnesota  side, 
Fere  it  forms  the  level  tract  known  as  the  “picnic  ground.” 

At  the  river  level,  at  the  upper  falls,  the  formation  of  pot-holes  is 
till  going  on.  The  most  remarkable  representatives  of  this  peculiar 
rosion  are  apparently  of  very  recent  origin.  A  large  rock  barrier  which 
ccupies  the  middle  of  the  St.  Croix  gorge  at  this  point  is  entirely  cov- 
red  with  them. 

In  addition  to  these  geologic  features,  collectors  will  obtain  speci- 
lens  of  fossils  from  the  shales  in  the  gorge ;  and  botanists  will  be  espe- 
iallv  interested  in  the  plant  inhabitants  of  the  spring  district  on  the 
Durth  terrace. 

EXCURSION  VI. 

'.iver  Plistory.  Falls  and  Abandoned  Channels.  (Time  two  hours.)  P.  11. 

Plan.  Start  from  the  toll  bridge  on  the  east  side  of  the  river.  Fol- 
nv  the  old  road  down  past  the  elbow  of  the  river  along  the  abandoned 
iver  channel  to  Thaxter  lake.  If  plenty  of  time  is  left  continue  along 
le  same  road  southward  a  mile  or  more  through  a  rock-bound  valley, 
rhich  constitutes  a  still  older  channel  and  which  may  be  seen  to  best 
dvantage  at  about  that  distance. 


34 


Suggestions.  It  will  be  seen  by  this  time  that  the  great  cliff  form¬ 
ing  the  south  wall  of  the  Dalles  must  have  been,  at  one  time,  an  island 
in  the  St.  Croix  river.  A  portion  of  the  river  flowed  through  the  gap 
where  the  road  runs  and  plunged  over  the  precipice  which  may  be  seen 
at  a  distance  of  four  or  five  rods  to  the  east.  The  great  hole  an  eighth 
of  a  mile  across,  which  lies  at  the  foot  of  this  fall,  belongs  to  the  accom  ¬ 
panying  erosion.  The  river  at  first  flowed  southwesterly  through  the 
earliest  channel,  abandoned  at  the  8oo-foot  line ;  and  later,  when  a  lower 
outlet  had  been  cut,  it  flowed  westerly  through  the  channel  now  occu¬ 
pied  by  Thaxter  lake.  Lake  Thaxter  is  a  good  example  of  a  river  lake 

EXCURSION  VII. 

The  St.  Croix  Moraine.  Drift  Accumulations.  (Time  one-half  day.)  P.  14 
Plan.  From  St.  Croix  Falls  follow  the  wagon  road  to  the  east  one 
or  two  miles  at  least  beyond  the  fair  ground  into  the  hill  country.  It 
may  be  studied  at  several  other  points  equally  well.  If  a  full  day  can 
be  spent,  take  the  road  to  the  north  from  the  “Soo”  depot  toward  Rock 
creek  trout  mere,  or  from  the  same  place  take  the  south  road  to  Poplar 
lake.  Either  road  passes  through  the  moraine  drift. 

Observations.  The  characters  of  the  drift  show  its  “eastern"  origin 
The  hilly  portion  forms  a  typical  moraine.  It  may  be  easily  crossed  as  it 
is  only  about  one  to  two  miles  wide.  This  is  a  part  of  the  celebrated 
“Kettle  Range”  and  the  so-called  kettle  holes  are  exhibited  abundantl) 
in  the  moraine.  Many  contain  water,  and  small  lakes  are  rather  plenti¬ 
ful.  They  probably  feed  the  numerous  springs  which  issue  at  the  high¬ 
er  levels.  Note  the  almost  entire  lack  of  erosion  here. 

Small  tracts  dependent  upon  peculiar  conditions  surrounding  th( 
last  glacial  invasion  and  the  retreat  of  the  ice  are  seen  here  and  there 
For  example,  the  level  area  at  1020  feet  just  east  of  St.  Croix  Falls,  anc 
the  evidences  of  erosion  along  the  road  toward  Dresser  Junction,  the 
deep  valley  of  Rock  creek  and  many  others  are  of  a  good  deal  of  interes 
if  one  succeeds  in  unraveling  their  history. 

EXCURSION  VIII. 

The  Lozver  Gorge.  A  River  Trip  to  Osceola.  (Time  one  day.) 

Plan.  Take  a  row  boat  to  Osceola  and  return.  Stop  at  Franconia 
at  conglomerate  cliff,  at  travertine  cave,  at  Osceola  falls,  at  Eagle  poin 
and  at  the  quarries  in  Osceola.  The  lower  Dalles  are  near  Franconia 
Suggestions.  The  gorge  can  be  studied  to  very  good  advantage 
Note  whether  there  is  any  evidence  of  its  pre-glacial  existence.  A 
Franconia  see  the  Lawrence  creek  gorge  and  get  some  fossils.  This  i 


ie  type  exposure  of  the  Franconia  sandstone.  At  Conglomerate  cliff 
ote  that  there  is  no  accompanying  diabase  ridge.  At  the  cave  just 
bove  this  place  get  specimens  of  compact  banded  travertine.  At  Eagle 
oint  see  the  Oneota  dolomite.  The  St.  Lawrence  shales  are  exposed  in 
le  creek  gorge  below  Osceola  falls.  Another  abandoned  channel  may 
e  seen  at  the  railway  station.  Good  fossils  may  be  secured  from  the 
ordan  sandstone  in  the  old  quarries  just  north  of  the  village.  Note  that 
:iis  is  the  northern  limit  of  the  Oneota  dolomite. 


EAGLE  POINT  NEAR  OSCEOLA, 

SHOWING  ONEOTA  DOLOMITE  CAPPING  THE  JORDAN  SANDSTONE. 


36 


EXCURSION  IX. 

The  Lozver  St.  Croix.  From  the  Dalles  to  Stillwater.  (Time  one  day.) 
Plan.  Take  the  steamboat  from  Taylor’s  Falls  to  Stillwater. 
Suggestions.  Note  the  succession  of  formations  which  follow  eacl 
other  in  the  river  bluffs, — The  Keweenawan  volcanic  rocks,  the  Dresbaci 
shales,  the  Jordan  sandstone,  the  Oneota  Dolomite. 

A  part  of  the  lower  gorge  is  pre-glacial.  Determine  its  beginning 

EXCURSION  X. 

A  Hunt  for  Fossils.  (Time  one  day.) 

Plan.  Visit  the  shales  in  the  river  gorge  at  St.  Croix  Falls,  th< 
conglomerate  outcrop  at  Taylor’s  Falls,  the  Lawrence  creek  gorg< 
at  Franconia  and  the  abandoned  sandstone  quarries  at  Osceola. 

Observations.  The  shales  at  St.  Croix  Falls  carry  the  best  sped 
mens  of  the  well-known  Lingulepis  acuminata  Con.  ( Lingulepis  pinnifor 
mis  Owen).  The  conglomerates  at  Taylor’s  Falls  contain  rare  types  o 
gasteropods.  Among  them  are  Hypseloconus  recurvus  Whitfield  ant 
Tryblidium  rectilaterale  Berkey,  besides  many  related  species  describet 
by  these  two  men.  Rarely  a  completely  coiled  form  belonging  to  Scae 
vogyra  or  Euomphalus  may  be  found.  Trilobites  are  more  common 
Several  species  of  Agraulus  are  reported  from  this  place.  The  rares 
species  are  Ptychoparia  calymenoides  Whitfield  and  Chcilocephalus  st 
croixensis  Berkey.  Only  two  of  the  former  and  one  of  the  latter  hav< 
been  reported.  Besides  these,  good  specimens  of  Obolclla  polita  Hall,  ; 
small  brachiopod,  are  abundant. 

At  Franconia  trilobites  are  almost  the  only  fossils  obtainable.  Bu 
some  of  them  are  splendid  specimens.  Dicelloccphalus  misa  Hall  is  th< 
largest  and  most  common  species. 

At  Osceola  the  best  specimens  are  of  species  of  Dicellocephalus  and  ; 
few  gasteropods,  among  which  Pleurotomaria  ( Holopea )  sweeti  Whitfielc 
is  the  best  known. 

COMBINATION  TRIPS  FOR  LARGE  ONE-DAY  EXCUR 

SIONS. 

COMBINATION  NO.  1.-10:30  A.  M.  to  1:00  P.  M. 

Itinerary.  The  train  will  usually  stop  on  such  occasions  a  mile  ou 
of  town  for  the  accommodation  of  the  excursion.  Start  at  one  of  th( 
sandstone  cliffs.  From  that  point  follow  the  railroad  in  to  the  stree 
crossing,  thence  by  the  street  over  the  hill  to  the  schoolhouse,  thence  b} 
way  of  the  depot  to  the  ravine  at  the  base  of  the  picnic  ground. 


37 


kings  to  see  and  places  to  look  for  them : 

1.  The  Franconia  sandstone  along  the  railway. 

2.  Cambrian  conglomerate  along  Mill  street  below  the  school- 

ouse. 

3.  Volcanic  Keweenawan  rocks  at  the  schoolhouse. 

4.  Volcanic  breccia  and  ash  (tuff)  one  block  west  of  the  school- 

ouse. 

5.  Eastern  and  Western  till  at  the  base  of  the  “picnic  ground/’ 

6.  The  highest  terrace,  the  “picnic  ground”  itself. 

Lunch— 1  :co  P.  M.  to  2:00  P.  M.  At  picnic  ground,  or  the  hotels, 

,r  in  the  Dalles. 

COMBINATION  NO.  II.  2:00  P.  M.  to  6:00  P.  M. 

Itinerary.  Follow  the  street  from  the  hotels  to  the  steamboat  land- 
lg  in  the  Dalles.  Pass  through  the  pot-hole  district  to  the  toll  bridge. 
Toss  the  river  and  follow  the  road  to  St.  Croix  Falls.  Reach  the  river 
gain  at  the  upper  falls.  Return  by  way  of  the  main  business  street  of 
t.  Croix  Falls  or  along  the  river  within  the  most  recent  gorge. 

,7 lings  to  see  and  places  to  look  for  them : 

1.  Great  pot-hole,  a  few  rods  northeast  of  the  boat  landing. 

2.  Separation  between  two  lava  flows,  along  the  street  leading  to 
ioat  landing. 

3.  The  Dalles,  pictured  rocks,  from  the  elbow  of  the  river. 

4.  Large  grinders,  in  one  of  the  great  “wells”  near  the  center  of 
he  pot-hole  district. 

5.  “The  old  man  of  the  Dalles,”  from  the  toll  bridge. 

6.  The  fourth  river  terrace,  along  the  road  at  the  flour  mill. 

7.  Good  spring  water,  and  plenty  of  it,  on  the  fourth  river  terrace. 

8.  The  second  river  terrace,  along  the  main  business  street  of  St. 
Croix  Falls. 

9.  Fossils — Lingnlepis  acuminata  Conrad,  in  the  river  gorge  above 

he  mill. 

10.  The  lower  Dresbach  shales,  in  the  river  gorge. 

11.  Pot-holes  in  process  of  formation,  at  the  upper  falls. 

12.  Calcite  crystals  (dog-tooth  and  nail-head  spar),  in  the  river 

-orge. 


38 


Fig.  4.  ST. LAWRENCE  SHALES. 

(reduced  one-third.) 

The  figure  is  reproduced  from  a  photograph  of  a  hand  specimen  collected  al 
Osceola  Falls.  The  darker  portions  represent  quartz  sand  ;  the  lighter  wav) 
bands  are  greenish  dolomitic  clay  shale.  To  satisfactorily  explain  the  origin  o 
such  a  rock  is  a  problem  of  considerable  complexity. 


EXPLANATION  TO  PLATE  L 

Fig.  1.  Lingulepis  pinniformis  Owen. 

Lingulepis  acuminata  Con.  (Walcott. ) 

Fig.  2.  Hypseloconus  ( Metoptoma )  recurvus  (Whitf. ),  var.  elongatus  Berkey. 
Fig.  3.  Agraulus  convexus  Whitf. 

Fig.  4.  Ptychoparia  calymenoides  (Whitf.),  (and  head  of  A.  convexus.) 
Fig.  5.  Agraulus  convexus  Whitf.,  (senile  individual. ) 

Fig.  6.  Hypselocoiius  stabilis  Berkey. 

Fig.  7.  Agraulus  convexus  Whitf.,  (average  size. ) 

Fig.  8.  Hypseloconus  recurvus  (Whitf.),  (small.) 

Fig.  9.  Euomphalus  strongi  (Whitf. ),  var.  sinistrorsus  Berkey. 

Fig.  10.  Hypseloconus  f ranconiensis  Berkey. 

Figs.  11-14.  Hypseloconus  recurvus  (Whitf.).  (three  different  forms.) 

Fig.  15.  Fragment  of  a  partially  coiled  form  of  undetermined  affinities. 

Fig.  16.  Hypseloconus  recurvus  { Whitf.) 

Fig.  17.  TryUidium  rectilaterale  Berkey . 

Fig  18.  TryUidium  convexum  Berkey. 

Fig.  19.  Gheilocephalus  st.  croixensis  Berkey. 

Fig.  20.  Slabs  showing  several  casts  of  Hypseloconus  recurvus. 

Fig.  21.  Hypseloconus  recurvus  (Whitf.),  var.  elongatus  Berkey. 


PLATE  I— CAMBRIAN  FOSSILS. 


40 


ACKNOWLEDGMENTS. 

I  am  indebted  to  the  St.  Paul  &  Duluth  R.  R.  for  several  of  the  cuts  used  b>j 
me  in  this  pamphlet.  Several  others  have  been  reprinted  by  permission  of  Th 
American  Geologist  in  whose  pages  the  writer  has  recently  used  them  in  illustration 
of  his  thesis  on  the  “Geology  of  The  St.  Croix  Dalles.”  And  I  take  this  oppor¬ 
tunity  of  acknowledging  my  obligations  to  Mr.  C.  E.  Stone  of  the  St.  P.  &  D. 
R.  R.,  and  Mr.  Geo.  H.  Hazzard,  Commissioner  of  the  Inter-State  Park,  for 
many  helpful  suggestions  in  the  prosecution  of  my  task. 

CHARLES  P.  BERKEY. 

Minneapolis,  June  23,  1898. 


PARLOR,  HOTEL  COCHECO. 


A.  E.  FREDEEN,  PROPRIETOR.  TAYLOR’S  FALLS,  MINN. 


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